High-gain antenna reflectors have been deployed into space from launch vehicles for several decades. The configurations of such reflectors have varied widely as material science developed and as the sophistication of technology and scientific needs increased.
Large diameter antenna reflectors pose particular problems both during deployment and post-deployment. Doubly-curved, rigid surfaces which are sturdy when in a deployed position cannot be folded for storage. Often, reflectors are stored one to two years in a folded, stored position prior to deployment. In an attempt to meet this imposed combination of parameters, large reflectors have been segmented into petals so that these petals could be stowed in various overlapped configurations. However, the structure required in deploying such petals has tended to be rather complex and massive, thus reducing the feasibility of such structures. For this reason, parabolic antenna reflecting surfaces larger than those that can be designed with petals typically employ some form of a compliant structure. Reference is made to U.S. Pat. 4,899,167, for its disclosure of such a system.
Responsive to the need for such a compliant structure, rib and mesh designs have been built, tested and used. However, such antennas tend to suffer from chording in both radial and circumferential directions. The use of mesh in such a configuration has an inherent disadvantage in diminishing the reflective quality of the resulting parabolic surface. Further, a mesh cannot be made to form a truly parabolic configuration. Reference is made to U.S. Pat. 3,707,720 for its disclosure of such a system.
Other antenna designs typically include a center post about which the petals are configured, much like an umbrella configuration. This also affects the reflective quality of the resulting surface, since the center portion typically is the point of optimum reflectance, which is then blocked by the center post. Thus, it is desirable to have a structure that is deployable from a compact, stored position to a parabolic, open position without the use of a center post. Reference is made to U.S. Pat. Nos. 3,286,270; 3,397,399 and 3,715,760 which disclose such systems.
Large lightweight flexible antennas have been formed from graphite fiber-reinforced plastic composite fabrics which can be wrapped around a spacecraft body into compact form, launched and caused to unfold relative to the spacecraft body to provide a satellite body having large reflective antennas.
For example, space satellites require antennas for signal reception and/or transmission. Such satellites and antennas must be relatively lightweight, strong, capable of being folded into compact condition, and capable of being activated remotely into unfolded, deployed condition in which they are operational for their intended purposes. It is generally desirable to use flexible antenna reflectors which are hingedly attached to the supporting spacecraft platform so that they can be folded up against the sides of the spacecraft into compact storage position during the launching of the spacecraft, and can be actuated remotely for unfolding and deployment into operating position in space. Such deployment may involve rotating the antenna supports on a hinge axis to unfold the reflectors to a position in which they extend perpendicular to the sides of the spacecraft, and also rotating the reflectors about a second axis, perpendicular to the first axis, to aim the reflectors in the direction of the signal source or target.
It is known to provide satellites with independent motorized units having complex gearing in order to accomplish remote orientation of their antennas about two different axes during deployment. Such motorized units are relatively heavy, subject to failure, expensive and less reliable than mechanical hinges. Therefore it is the principal object of the present invention to provide a simplified dual-axis hinge assembly which overcomes the problems of prior-known motor-driven dual axis hinge assemblies, particularly for space satellite use.
There is a need for relatively simple, lightweight, mechanical hinge assemblies having two integrated axes of rotation which co-operate to rotate and extend a supported element, such as a space antenna, to a desired radial position about a first axis while simultaneously rotating the supported element to a desired position about a second axis which extends perpendicular to the first axis to aim the reflector in a desired direction.